Spray drying apparatus



Aug, 9, 1949.

Filed March 7, 1945 0.. 'T. PIEFE R SPRAY DRYING, APPARATUS 2 Sheets-Sheet 1 'I'TORNEYS Aug. 9, 1949.

o. T. PIEPER SPRAY DRYING APPARATUS 2 Sheets-Sheet 2 Filed March 7, 1945 INVENTQR O lie BY [2 Patented Aug. 9, 1949 UNITED stares PATENT; OFFICE I 2,478,779 SPRAY DRYING APPARATUS Oliver '1. Pieper, Wilmington, DcL, assignor to American Dyewood Company, New York, N. Y., a corporation of Pennsylvania Application March 7, 1945, Serial No. 581,477

3 Claims.

This invention relates to spraydrying and particularly to improvements in the method of separating material in a dry condition from liquids containing such. material and to apparatus therefor.

Spray drying, in which liquid is distributed into a current of heated gas such for example as combustion products, with or without added air. for the purpose of rapidly evaporating the liquid and obtaining a dry product, has been practised for many years with various types of apparatus. The most modern and efiective apparatus utilizes a whirling disc or wheel" to which the liquid is fed and from which it is distributed by centrifugal force applied by rapid rotation of the wheel into an atmosphere to which heated gases are continuously delivered. One of the problems which has not been solved satisfactorily heretofore is that of securing uniform distribution of the heated gases to the chamber in which the drying is effected. Lack of uniform distribution of the gases results in failure to evaporate all of the liquid in portions of the material, and deposits of partially evaporated material are built up on the walls of the evaporation chamber. This in' turn necessitates frequent stoppage of the apparatus for cleaning and additional expense due to cleaning and to the loss of material which is not recovered in the desired form.

These andother disadvantages of the known types of apparatus have limited the application of spray drying, which in many cases has proved to be uneconomical.

It is the object of the present invention to provide an improved method of spray drying in which uniformity of distribution of the heated gases is maintained and the disadvantages mentionedare avoided.

Another object of the invention is the provision of an improved apparatusembodying novel means ,for securing uniform distribution of the heated'gases in the evaporation chamber to effect rapid and complete evaporation of allof the liquid delivered to the chamber.

A further object of the invention is the provision of improved means for generating and distributing heated gases, the distribution being symmetrical with respect to the axis of distribution of the liquid so that uniform contact of the heated gases with the liquid is attained.

Other objects and advantages of theinvention will be apparent as it is better understood byreference to the following specification and the accompanying drawing, in which Fig. 1 is a diagrammatic representation of a portion of a spray chamber with the apparatus for generating and distributing heated gases arconstruction of the wheel form no part of the present invention, being described in my copending application Ser. No. 581,476, filed March 7, 1945 The wheelis disposed ina well a m the top of the chamber 4 which communicates through passages I with the interior of the chamber so that cool air may circulate about the driving mechanism for the wheel (not shown) and thereafter enter the chamber in such a manner as to protect the mechanism from heat supplied through the heated gases which are introduced to effect evaporation.

In order to accomplish the purpose of the invention, the source of heated gases must be disposed axially'with respect to thewheei 5 either above or below the chamber 4. In the drawing, the source of heated gases is shown above the chamber, although the alternative position is equally effective. sential in order that distribution of the heated gases may be effected through a plurality of symmetrically arranged flues which deliver the heated gases at symmetrically disposed inlets to the chamber 4.

The heated gases are produced by combustion of any suitable fuel, preferably oil or gas, introduced through a burner 8 to a combustion chem ber surrounded by a shell 9 of heat resistant brick or other suitable material. Air for combustion enters through openings ID at the bottom of the chamber, and the heated combustion gases escape through openings II at the top thereof. The combustion chamber or furnace is preferably surrounded by a shell l2 affording a circumferential flue l3 through which additional air may circulate to mix with the hot combustion gases to reduce the temperature thereof. By regulation of the burner 8, the proper volume of heated gases at the required temperature can be delivered through the throat II.

In initiating the operation, it is necessary to discharge the mixture of combustion products and air to the atmosphere until the proper. tem- The axial arrangement is es-' 3 perature has been attained. For that inn-pose. a cylindrical valve i5 carrying a circumferential flange i6 is supported for movement above the throat I l and is adapted to be actuated through a bar I'I having a stem l8 and link is which may symmetrically arranged flues 25 which deliver the air to the chamber 4. When the valve i5 is raised to the position indicated in the drawing, the upper end thereof is closed by a plate 25 so that gases from the furnace can no longer escape to the chimney 23. At the same time, the cold air inlets 24 are closed. The heated gases from the furnace are then diverted to the flues 25.

The inlets to the flues 25 are of reduced diamacra'na r eter due to the position of the flange it so that the mixture of combustion gases and air passes through throats of reduced size and expands into the flues 25. Thisarrangement ensures thorough mixture :of the auxiliary air with the combustion products and a uniform composition of the heated gaseous mixture flowing through the flues 25. The symmetrical arrangement of the flues ensures the distribution of precisely equal partsof the heated gases through the respective flues. Although four are shown in thedrawing, any number of flues may be used, provided they are symmetrically disposed with respect to the axis of the furnace and of the wheel 5 her 4.

in the spray chamand 4 Various changes may arrangement of the parts, it being essential, however, as hereinbefore indicated, that the source of heated gases be disposed axially with respect to the distribution wheel and that the dues carrying the heated gases be symmetrically arranged about the axis in order to avoid inequalities in distribution of the heated gases.

I claim:

1. In an apparatus for delivering heated gases for. contact with a liquid spray, the combination of a spray distributor, a combustion furnace longitudinally, axially aligned with reference to the distributor, and a plurality of flues symmetrically disposed about the axis of the distributor communicating with the furnace and terminating about the distributor to deliver combustion products adjacent thereto and substantially parallel to the axis thereof.

2. In an apparatus for delivering heated gases for contact with a liquid spray, the combination of a spray distributor, a combustion furnace longitudinally, axially aligned with reference to the distributor, a movable 'valve adapted to control the flow of combustion products from the furnace and a plurality of flues symmetrically disposed about the axis of the distributor communicating with the furnace and terminating about the distributor to deliver combustion products adjacent thereto and substantially parallel to the axis thereof.

To ensure further subdivision of the heated I:

gases, each of the flues 25 may beprovidedwith a partition 26 extending through an enlarged seetion 21 at the lower end of each of the flues. partitions divide the vheated gases flowing through the flues 25 into equal parts. The .en-

larged sections 21 terminate in inlets 28 sym metrically arranged about the well 6. Thus. allquot parts of the heated gases are delivered uniformly and symmetrically intothe chamber 4 about the wheel 5 and consequently-to the liquid delivered by the wheel in a uniform manner laterally and in all directions about the axis. By thus ensuring the uniform livery 'of the heated gases, the disa'dvantages'inherent in spray drying apparatus as'heretofore known are avoided. It is possible to secure rapid and complete drying ofthe solid particles and to avoid the accumulation of partially dried'xnaterials on the walls of the spray chamber;

The

and symmetrical deabout the distributor to "40 3. In an apparatus for delivering heated gases for contact with a liquid spray; of a spraydistributor, a combustion furnace longitudinally, axially aligned with' reference to the distributor, and a plurality of flues symmetrically disposed about the axis of the distributor communicating with'the furnace and terminating deliver combustion products adjacent thereto and substantially parallel to the axis thereof, the flues having partitions therein to subdivide the tion products,

, I OLIVER T. PIEPER.

summons crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 954,451 Merrell Apr. 12, 1910 1,779,296 A Spross Oct. 21, 1930 1,966,084 Werner July 10, 1934 2,280,073- Hall Apr. 21, 1942 Dennis 2,375,288 May 8, 1945 be made in the structure the combination streams of combus- 

